With development of millimeter-wave wireless communication technology and interest in automotive safety technology, demand for a vehicular radar technology is increasing rapidly. A vehicular radar apparatus is mounted on an outer side of a vehicle, and may detect or track a distance, speed, and angle of a target apparatus through radio wave transmission and reception. Nowadays, radar of a frequency modulated continuous wave (FMCW) method, which may be implemented with a relatively simple circuit configuration and a low radio wave output in 24 GHz or 77 GHz band, has been adopted as a vehicular radar apparatus so that a vehicle having functions of front detection, side and rear detection, and an automatic cruise control has been developed.
In components constituting a reliable vehicular radar apparatus, an array antenna is a core component functioning to transmit and receive a radar wave, and has a phase array antenna structure in order to distinguish relative positions and speeds of an obstacle and a vehicle. For the front detection and automatic cruise control, an antenna is used which divides and detects an angular area of a narrow range very precisely, and for the side and rear detection, an antenna is required which is divides and detects an angular area of wide range.
Meanwhile, a vehicular radar apparatus includes an antenna configured to transmit and receive radio waves, internal electronic components such as a millimeter-wave radio frequency integrated circuit (RFIC), and a radome configured to protect the same. The radome mechanically protects internal electronic components of a vehicular radar apparatus from external environment, and functions to minimize loss of radio waves transmitted to outside or received from the outside.
Since a vehicular radar apparatus installed on a rear side of a vehicle is necessary to detect a side and rear of a vehicle, which are not seen by a side mirror, the vehicular radar apparatus is required to have a very wide detection angle of field of view (FOV) of 150 degrees or more. For this, there is an attempt to use a wide-angle antenna having a wide beam width, but it is difficult to obtain a detection angle of the FOV of 150 degrees or more with the wide-angle antenna only.